Will I damage a hose if I clamp it shut to do a cylinder leak down test?

[lhfarm]

Why not just disconnect the bottom hose and see if any fluid comes out of it?

Aaron Z

Fluid does come out. So I'm assuming that is the result of a damaged seal.

I have been fighting the hydraulic system for months, with pump seal leaks, suction side leaks, and a faulty control valve. I have a feeling that I damaged the cylinder in all my efforts to correct those problems. The good news is that I now have a lot more hard earned understanding (can't call it knowledge yet) of how this system is supposed to work.

Thanks,

 

[aczlan]

Fluid does come out. So I'm assuming that is the result of a damaged seal.

I have been fighting the hydraulic system for months, with pump seal leaks, suction side leaks, and a faulty control valve. I have a feeling that I damaged the cylinder in all my efforts to correct those problems. The good news is that I now have a lot more hard earned understanding (can't call it knowledge yet) of how this system is supposed to work.

Yep, if the bottom hose returns directly to the tank (no valve) and you are getting fluid there, you have bad seals in the cylinder.
Probably just age/wear as it would be hard to damage those seals unless you open the cylinder up.

Aaron Z

 

[CJONE]

Put a ball valve in line and close it. CJ

 

[RickB]

Put a ball valve in line and close it. CJ

As if that would help the cylinder stop settling.

 

[LD1]

If its a DA cylinder being used as a SA cylinder, and the hose connected to the port that is NOT being pressurized to make the lift work, is leaking fluid out when the lift leaks down....the piston seals are most certainly bad.

Since its being used as a SA cylinder, putting a valve on that "vent" line will do little. Because I assume where it returns to tank is ABOVE the level of the oil in the tank. So when you lower the lift, that vent line is under vacuum and drawing air. Valving it off, if the piston is leaking by, will just compress that air.

Not to mention the issues you would have trying to cycle the lift up and down while in use, with the vent side blocked off.

Sounds like a new cylinder or a rebuild is in order.

 

[lhfarm]

If its a DA cylinder being used as a SA cylinder, and the hose connected to the port that is NOT being pressurized to make the lift work, is leaking fluid out when the lift leaks down....the piston seals are most certainly bad.

Since its being used as a SA cylinder, putting a valve on that "vent" line will do little. Because I assume where it returns to tank is ABOVE the level of the oil in the tank. So when you lower the lift, that vent line is under vacuum and drawing air. Valving it off, if the piston is leaking by, will just compress that air.

Not to mention the issues you would have trying to cycle the lift up and down while in use, with the vent side blocked off.

Sounds like a new cylinder or a rebuild is in order.

After years of trying to figure out why the "bleeder hose" (as labeled in the 1947 installation instructions) dumped into the top of the reservoir, it finally dawned on me. This lift is on a 1949 jeep and it sets under the body. The cylinder is just a few inches above the ground. If the SA cylinder had used a standard "drain" hole or breather port, it would have been exposed to all the dirt and dust that comes with plowing and other ground work. They used the extra space in the top of the reservoir for breather purposes to minimize the exposure to the environment. Pretty slick once I thought about it.

 

[aczlan]

After years of trying to figure out why the "bleeder hose" (as labeled in the 1947 installation instructions) dumped into the top of the reservoir, it finally dawned on me. This lift is on a 1949 jeep and it sets under the body. The cylinder is just a few inches above the ground. If the SA cylinder had used a standard "drain" hole or breather port, it would have been exposed to all the dirt and dust that comes with plowing and other ground work. They used the extra space in the top of the reservoir for breather purposes to minimize the exposure to the environment. Pretty slick once I thought about it.

It also returns any fluid that leaks past the piston seals back to the tank.

Aaron Z

 

[LD1]

It also returns any fluid that leaks past the piston seals back to the tank.

Aaron Z

That is probably the main reason.

We have some SA cylinder hoists at work. Those brass breather plugs are great at letting out enough air to ensure operation. But when a piston seal starts leaking by, the first thing that happens is it blows the sintered brass breather apart as it cannot allow enough fluid through as fast as the hoist wants to move.

 

[aczlan]

That is probably the main reason.

We have some SA cylinder hoists at work. Those brass breather plugs are great at letting out enough air to ensure operation. But when a piston seal starts leaking by, the first thing that happens is it blows the sintered brass breather apart as it cannot allow enough fluid through as fast as the hoist wants to move.

Yep. I have a SA hoist cyinder under a dump wagon and it needs new seals. When you hit the top, it starts blowing fluid out of the vent (which now has a plastic pipe plug that has a 3/16" hole drilled in it and a cotter pin in the hole.

Aaron Z

 

[CJONE]

As if that would help the cylinder stop settling.

If the cylinder is leaking internally it won't. But if the valve is leaking, it will. It is how you isolate the problem. Some of you wonder why people are not willing to help. Hummm, I wonder? CJ